Algae: Biofuel of the Future?

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Oil produced by algae growing in an area roughly the size of
South Carolina could replace a sizable chunk of the oil the
United States imports for transportation, according to a new
analysis that also contends that water use — a drawback to algal
biofuel — could be minimized.

"Algae has been a hot topic of biofuel discussions recently, but
no one has taken such a detailed look at how much America could
make, and how much water and land it would require, until now,"
said Mark Wigmosta, a U.S. Department of Energy hydrologist who
was the lead researcher for the analysis. "This research provides
the groundwork and initial estimates needed to better inform
renewable
energy decisions."

The researchers concluded that farmed algae could produce 21
billion gallons of oil, fulfilling a federal goal set for
advanced biofuel production in 2022. Growing algae domestically
would help reduce the U.S. dependence on foreign oil — in 2009,
slightly more than half of the
petroleum used in the U.S. came from abroad.

Algae grown in freshwater ponds in the country's most sunny and
humid climates — the Gulf Coast, the southeastern seaboard and
the Great Lakes — would require the least water, the researchers
said.

Algae have some important advantages as a source of biofuel,
which in this case would be made by extracting and refining oils
called lipids produced by the simple plants. Algae can produce 80
times more oil than an equal area of corn does. And unlike with
corn, which is used to make ethanol, algae grown for biofuel
production wouldn't interfere with a food crop, since algae
aren't a widespread food source. Algae also consume carbon
dioxide, the primary greenhouse gas, and can grow in (and clean)
municipal wastewater.

But algae, like other biofuels, require a lot of water to
produce. This is not an issue with conventional petroleum, which
is extracted from the Earth, not grown. [ The
Real Costs of Renewable Energy ]

Wigmosta, who works at the DOE's Pacific Northwest National
Laboratory, and his colleagues set out to assess just how much
algae-derived oil the United States could produce and how much
water that would require. Using geographic data, they identified
areas suited for growing algae in freshwater ponds. Using weather
data to estimate amount of sunlight (since algae rely on
photosynthesis to grow) and temperature, the researchers
calculated the amount of algae that could be produced hourly at
each specific site.

They also estimated how much water would need to be replaced due
to evaporation over 30 years, based on growing algae in open,
outdoor, freshwater ponds using current technology.

They calculated that enough algae to produce 21 billion gallons
of oil — 17 percent of the petroleum that the U.S. imported in
2008 for transportation fuels — could be grown on lands
roughly totaling the size of South Carolina, using 350
gallons of water per gallon of oil produced. This amounts to a
quarter of the water currently used for agriculture.

"Water is an important consideration when choosing a biofuel
source," Wigmosta said. "And so are many other factors. Algae
could be part of the solution to the nation's energy puzzle if
we're smart about where we place growth ponds, and the technical
challenges to achieving commercial-scale algal biofuel production
are met."